I need to use the datapump will parallelism. I understand that the parallelism value will be based on the number of CPUs. In our machine, we can see 2 core processor on the server properties. But the systeminfo output shows it has 8 logical processors. This means there are 16 processors. I was able to confirm this on the computer management device as well.

To set the value for "PARALLEL" option, do I need to go with the overall logical processors count (16) or core processors (2)?

The more resources consumed by datapump, the fewer resources available for OLTP users.
What is advantage if datapump completes a few minutes sooner but the online users can't work during datapump operation?